Numbers 19:17-19

¹⁷And for the unclean person they shall take of the ashes of the burnt sin offering, and put spring water upon it in a vessel.

¹⁸And a man who is clean shall take hyssop, and dip it in the water, and sprinkle upon the tent, and upon every vessel, and upon the persons who are there, and upon him who had touched the bone, or the slain, or the dead body, or the grave.

¹⁹And the clean person shall sprinkle the unclean on the third day, and on the seventh day; and on the seventh day he shall be clean; and shall sprinkle his raiment, and wash with water, and at the evening he shall be clean.